Ultrasound imaging or ultrasonography is an ultrasound-based diagnostic imaging technique used to visualize subcutaneous body structures including tendons, muscles, joints, vessels and internal organs for possible pathology or lesions. Obstetric sonography is commonly used during pregnancy and is widely recognized by the public. Various other diagnostic and therapeutic applications are practiced in medicine.
In order to obtain a good quality image of the body structures of interest, it is necessary for the pulses of sound emitted by an ultrasound transducer to be passed into the body and received from the body without interference. The materials that form the face of the transducer are chosen to enable the sound to be transmitted efficiently into the body. In addition, a water-based gel (hydrogel) is placed between the patient's skin and the probe to ensure good acoustic coupling. The gel allows the probe to be moved over the skin whilst maintaining the desired acoustic coupling so that different areas can be imaged as required.
In recent times, a number of innovative applications for ultrasound imaging have been developed where it is desirable to fix an ultrasound probe in a single position for a sustained period of time. WO 2004/052431 and WO 2009/044151 disclose the use of an ultrasound Doppler technique to monitor an injection and provide a signal to indicate the possibility of extravasation. The ultrasound Doppler probe is located in a single position over a vein. WO 2004/049951 discloses a respiration monitoring apparatus where an array of ultrasound transducers is located over the diaphragm. With this apparatus, the acoustic impedance of the tissue adjacent to each transducer is used to determine the presence of aerated and non-aerated tissue, and the degree of lung inspiration is thereby determined. In these applications there is a need to secure the ultrasound probe to the skin.
In addition to securing an ultrasound probe in a single position, it is highly desirable to be able to do this in such a way that all transducers in the probe, which may be an array for placement over a relatively large skin surface, are provided with an good acoustic connection with the body structure of interest.
Traditional hydrogels used with traditional ultrasound probes are not able to provide the required adhesion for sustained and secure coupling to the skin.